Lettuce variety &#39;roscoe&#39;

ABSTRACT

New lettuce variety designated ‘Roscoe’ is described. ‘Roscoe’ is a lettuce variety exhibiting stability and uniformity.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/976,836, filed Feb. 14, 2020, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of plant breeding. Inparticular, this invention relates to a new lettuce, Lactuca sativa,variety designated ‘Roscoe’.

BACKGROUND OF THE INVENTION

Cultivated forms of lettuce belong to the highly polymorphic speciesLactuca sativa that is grown for its edible head and leaves. As a crop,lettuce is grown commercially wherever environmental conditions permitthe production of an economically viable yield. For planting purposes,the lettuce season is typically divided into three categories (i.e.,early, mid, and late), with coastal areas planting from January toAugust, and desert regions planting from August to December. Freshlettuce is consumed nearly exclusively as fresh, raw product andoccasionally as a cooked vegetable.

Lactuca sativa is in the Cichorieae tribe of the Asteraceae (Compositae)family. Lettuce is related to chicory, sunflower, aster, dandelion,artichoke, and chrysanthemum. Sativa is one of about 300 species in thegenus Lactuca. There are seven different morphological types of lettuce.The crisphead group includes the iceberg and batavian types. Iceberglettuce has a large, firm head with a crisp texture and a white orcreamy yellow interior. The batavian lettuce predates the iceberg typeand has a smaller and less firm head. The butterhead group has a small,soft head with an almost oily texture. The romaine, also known as coslettuce, has elongated upright leaves forming a loose, loaf-shaped headand the outer leaves are usually dark green. In North America, romaineis sold as whole heads with the outer leaves attached or as hearts thathave had the outer leaves removed and are often packaged together. Leaflettuce, also known as cutting lettuce, comes in many varieties, none ofwhich form a head, and include the green oak leaf variety. Latinlettuce, also known as grasse-type lettuce, looks like a cross betweenromaine and butterhead. Stem lettuce has long, narrow leaves and thick,edible stems. Oilseed lettuce is a type grown for its large seeds thatare pressed to obtain oil.

Lettuce is an increasingly popular crop. Worldwide lettuce consumptioncontinues to increase. As a result of this demand, there is a continuedneed for new lettuce varieties. In particular, there is a need forimproved lettuce varieties that are stable, high yielding, andagronomically sound.

SUMMARY OF THE INVENTION

In order to meet these needs, the present invention is directed to animproved lettuce variety.

In one embodiment, the present invention is directed to lettuce, Lactucasativa, seed designated as ‘Roscoe’ having NCIMB Accession Number X1. Inone embodiment, the present invention is directed to a Lactuca sativalettuce plant and parts isolated therefrom produced by growing ‘Roscoe’lettuce seed. In another embodiment, the present invention is directedto a Lactuca sativa plant and parts isolated therefrom having all thephysiological and morphological characteristics of a Lactuca sativaplant produced by growing ‘Roscoe’ lettuce seed having NCIMB AccessionNumber X1. In still another embodiment, the present invention isdirected to an F₁ hybrid Lactuca sativa lettuce seed, plants grown fromthe seed, and a heart isolated therefrom having ‘Roscoe’ as a parent,where ‘Roscoe’ is grown from ‘Roscoe’ lettuce seed having NCIMBAccession Number X1.

Lettuce plant parts include lettuce hearts, lettuce leaves, parts oflettuce leaves, pollen, ovules, flowers, and the like. In anotherembodiment, the present invention is further directed to lettuce hearts,lettuce leaves, parts of lettuce leaves, flowers, pollen, and ovulesisolated from ‘Roscoe’ lettuce plants. In another embodiment, thepresent invention is further directed to tissue culture of ‘Roscoe’lettuce plants, and to lettuce plants regenerated from the tissueculture, where the plant has all of the morphological and physiologicalcharacteristics of ‘Roscoe’ lettuce plants.

In still another embodiment, the present invention is further directedto packaging material containing ‘Roscoe’ plant parts. Such packagingmaterial includes but is not limited to boxes, plastic bags, etc. The‘Roscoe’ plant parts may be combined with other plant parts of otherplant varieties.

In yet another embodiment, the present invention is further directed toa method of selecting lettuce plants, by (a) growing ‘Roscoe’ lettuceplants where the ‘Roscoe’ plants are grown from lettuce seed havingNCIMB Accession Number X1 and (b) selecting a plant from step (a). Inanother embodiment, the present invention is further directed to lettuceplants, plant parts and seeds produced by the lettuce plants where thelettuce plants are isolated by the selection method of the invention.

In another embodiment, the present invention is further directed to amethod of breeding lettuce plants by crossing a lettuce plant with aplant grown from ‘Roscoe’ lettuce seed having NCIMB Accession Number X1.In still another embodiment, the present invention is further directedto lettuce plants, lettuce parts from the lettuce plants, and seedsproduced therefrom where the lettuce plant is isolated by the breedingmethod of the invention.

In another embodiment, the present invention is directed to methods forproducing a male sterile lettuce plant by introducing a nucleic acidmolecule that confers male sterility into a lettuce plant produced bygrowing ‘Roscoe’ lettuce seed, and to male sterile lettuce plantsproduced by such methods.

In another embodiment, the present invention is directed to methods ofproducing an herbicide resistant lettuce plant by introducing a geneconferring herbicide resistance into a lettuce plant produced by growing‘Roscoe’ lettuce seed, where the gene confers resistance to an herbicideselected from glyphosate, sulfonylurea, imidazolinone, dicamba,glufosinate, phenoxy proprionic acid, L-phosphinothricin, cyclohexone,cyclohexanedione, triazine, and benzonitrile. Certain embodiments arealso directed to herbicide resistant lettuce plants produced by suchmethods.

In another embodiment, the present invention is directed to methods ofproducing a pest or insect resistant lettuce plan by introducing a geneconferring pest or insect resistance into a lettuce plant produced bygrowing ‘Roscoe’ lettuce seed, and to pest or insect resistant lettuceplants produced by such methods. In certain embodiments, the geneconferring pest or insect resistance encodes a Bacillus thuringiensisendotoxin.

In another embodiment, the present invention is directed to methods ofproducing a disease resistant lettuce plant by introducing a geneconferring disease resistance into a lettuce plant produced by growing‘Roscoe’ lettuce seed, and to disease resistant lettuce plants producedby such methods.

In another embodiment, the present invention is directed to methods ofproducing a lettuce plant with a value-added trait by introducing a geneconferring a value-added trait into a lettuce plant produced by growing‘Roscoe’ lettuce seed, where the gene encodes a protein selected from aferritin, a nitrate reductase, and a monellin. Certain embodiments arealso directed to lettuce plants having a value-added trait produced bysuch methods.

In another embodiment, the present invention is directed to methods ofintroducing a desired trait into lettuce variety ‘Roscoe’, by: (a)crossing a ‘Roscoe’ plant, where a sample of ‘Roscoe’ lettuce seed wasdeposited under NCIMB Accession Number X1, with a plant of anotherlettuce variety that contains a desired trait to produce progeny plants,where the desired trait is selected from male sterility; herbicideresistance; insect or pest resistance; modified bolting; and resistanceto bacterial disease, fungal disease or viral disease; (b) selecting oneor more progeny plants that have the desired trait; (c) backcrossing theselected progeny plants with a ‘Roscoe’ plant to produce backcrossprogeny plants; (d) selecting for backcross progeny plants that have thedesired trait and all of the physiological and morphologicalcharacteristics of lettuce variety ‘Roscoe’; and (e) repeating steps (c)and (d) two or more times in succession to produce selected third orhigher backcross progeny plants that comprise the desired trait. Certainembodiments are also directed to lettuce plants produced by suchmethods, where the plants have the desired trait and all of thephysiological and morphological characteristics of lettuce variety‘Roscoe’. In certain embodiments, the desired trait is herbicideresistance and the resistance is conferred to an herbicide selected fromglyphosate, sulfonylurea, imidazolinone, dicamba, glufosinate, phenoxyproprionic acid, L-phosphinothricin, cyclohexone, cyclohexanedione,triazine, and benzonitrile.

In another embodiment, the present invention provides for single geneconverted plants of ‘Roscoe’. The single transferred gene may preferablybe a dominant or recessive allele. Preferably, the single transferredgene will confer such traits as male sterility, herbicide resistance,insect or pest resistance, modified fatty acid metabolism, modifiedcarbohydrate metabolism, resistance for bacterial, fungal, or viraldisease, male fertility, enhanced nutritional quality, and industrialusage.

In a further embodiment, the present invention relates to methods fordeveloping lettuce plants in a lettuce plant breeding program usingplant breeding techniques including recurrent selection, backcrossing,pedigree breeding, restriction fragment length polymorphism enhancedselection, and genetic marker enhanced selection. Seeds, lettuce plants,and parts thereof, produced by such breeding methods are also part ofthe invention.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference bystudy of the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings will be provided by the office upon request and paymentof the necessary fee.

FIGS. 1A-1D show photos of lettuce variety ‘Roscoe’. FIG. 1A shows thefourth leaf from a 20 day-old seedling of lettuce variety ‘Roscoe’. FIG.1B shows a top view of a plant with harvest-mature outer leaves oflettuce variety ‘Roscoe’. FIG. 1C shows a side view of a plant oflettuce variety ‘Roscoe’. FIG. 1D shows a longitudinal cross-sectionalview of a harvest-mature plant of lettuce variety ‘Roscoe’.

FIG. 2 shows a longitudinal cross-sectional view of a harvest-matureplant of lettuce variety ‘Arroyo’.

FIG. 3 shows a longitudinal cross-sectional view of a harvest-matureplant of lettuce variety ‘Green Forest’.

DETAILED DESCRIPTION OF THE INVENTION

There are numerous steps in the development of novel, desirable lettucegermplasm. Plant breeding begins with the analysis of problems andweaknesses of current lettuce germplasms, the establishment of programgoals, and the definition of specific breeding objectives. The next stepis selection of germplasm that possess the traits to meet the programgoals. The goal is to combine in a single variety or hybrid an improvedcombination of desirable traits from the parental germplasm. Theseimportant traits may include increased heart size and weight, higherseed yield, improved color, resistance to diseases and insects,tolerance to drought and heat, and better agronomic quality.

Choice of breeding or selection methods can depend on the mode of plantreproduction, the heritability of the trait(s) being improved, and thetype of variety used commercially (e.g., F₁ hybrid variety, purelinevariety, etc.). For highly heritable traits, a choice of superiorindividual plants evaluated at a single location will be effective,whereas for traits with low heritability, selection should be based onmean values obtained from replicated evaluations of families of relatedplants. Popular selection methods commonly include pedigree selection,modified pedigree selection, mass selection, and recurrent selection.

The complexity of inheritance influences choice of the breeding method.Backcross breeding is used to transfer one or a few favorable genes fora highly heritable trait into a desirable variety. This approach hasbeen used extensively for breeding disease-resistant varieties. Variousrecurrent selection techniques are used to improve quantitativelyinherited traits controlled by numerous genes. The use of recurrentselection in self-pollinating crops depends on the ease of pollination,the frequency of successful hybrids from each pollination, and thenumber of hybrid offspring from each successful cross.

Each breeding program may include a periodic, objective evaluation ofthe efficiency of the breeding procedure. Evaluation criteria varydepending on the goal and objectives, and can include gain fromselection per year based on comparisons to an appropriate standard, theoverall value of the advanced breeding lines, and the number ofsuccessful varieties produced per unit of input (e.g., per year, perdollar expended, etc.).

Promising advanced breeding lines may be thoroughly tested and comparedto appropriate standards in environments representative of thecommercial target area(s) for at least three years. The best lines canthen be candidates for new commercial varieties. Those still deficientin a few traits may be used as parents to produce new populations forfurther selection. These processes, which lead to the final step ofmarketing and distribution, may take from ten to twenty years from thetime the first cross or selection is made.

One goal of lettuce plant breeding is to develop new, unique, andgenetically superior lettuce varieties. A breeder can initially selectand cross two or more parental lines, followed by repeated selfing andselection, producing many new genetic combinations. Moreover, a breedercan generate multiple different genetic combinations by crossing,selfing, and mutations. A plant breeder can then select which germplasmsto advance to the next generation. These germplasms may then be grownunder different geographical, climatic, and soil conditions, and furtherselections can be made during, and at the end of, the growing season.

The development of commercial lettuce varieties thus requires thedevelopment of parental lettuce varieties, the crossing of thesevarieties, and the evaluation of the crosses. Pedigree breeding andrecurrent selection breeding methods may be used to develop varietiesfrom breeding populations. Breeding programs can be used to combinedesirable traits from two or more varieties or various broad-basedsources into breeding pools from which new varieties are developed byselfing and selection of desired phenotypes. The new varieties arecrossed with other varieties and the hybrids from these crosses areevaluated to determine which have commercial potential.

Pedigree breeding is generally used for the improvement ofself-pollinating crops or inbred lines of cross-pollinating crops. Twoparents which possess favorable, complementary traits are crossed toproduce an F₁. An F₂ population is produced by selfing one or severalF_(1S) or by intercrossing two F_(1S) (sib mating). Selection of thebest individuals is usually begun in the F₂ population. Then, beginningin the F₃, the best individuals in the best families are selected.Replicated testing of families, or hybrid combinations involvingindividuals of these families, often follows in the F₄ generation toimprove the effectiveness of selection for traits with low heritability.At an advanced stage of inbreeding (i.e., F₆ and F₇), the best lines ormixtures of phenotypically similar lines are tested for potentialrelease as new varieties.

Mass and recurrent selections can be used to improve populations ofeither self- or cross-pollinating crops. A genetically variablepopulation of heterozygous individuals is either identified or createdby intercrossing several different parents. The best plants are selectedbased on individual superiority, outstanding progeny, or excellentcombining ability. The selected plants are intercrossed to produce a newpopulation in which further cycles of selection are continued.

Backcross breeding may be used to transfer genes for a simply inherited,highly heritable trait into a desirable homozygous cultivar or line thatis the recurrent parent. The source of the trait to be transferred iscalled the donor parent. The resulting plant is expected to have theattributes of the recurrent parent (e.g., cultivar) and the desirabletrait transferred from the donor parent. After the initial cross,individuals possessing the phenotype of the donor parent are selectedand repeatedly crossed (backcrossed) to the recurrent parent. Theresulting plant is expected to have the attributes of the recurrentparent (e.g., cultivar) and the desirable trait transferred from thedonor parent.

In some embodiments, the single-seed descent procedure may refer toplanting a segregating population, harvesting a sample of one seed perplant, and using the one-seed sample to plant the next generation. Whenthe population has been advanced from the F₂ to the desired level ofinbreeding, the plants from which lines are derived will each trace todifferent F₂ individuals. The number of plants in a population declineswith each generation due to failure of some seeds to germinate or someplants to produce at least one seed. As a result, not all of the F₂plants originally sampled in the population will be represented by aprogeny when generation advance is completed.

In addition to phenotypic observations, the genotype of a plant can alsobe examined. There are many laboratory-based techniques known in the artthat are available for the analysis, comparison and characterization ofplant genotype. Such techniques include, without limitation, IsozymeElectrophoresis, Restriction Fragment Length Polymorphisms (RFLPs),Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily PrimedPolymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting(DAF), Sequence Characterized Amplified Regions (SCARs), AmplifiedFragment Length polymorphisms (AFLPs), Simple Sequence Repeats (SSRs),which are also referred to as Microsatellites), and Single NucleotidePolymorphisms (SNPs).

Molecular markers can also be used during the breeding process for theselection of qualitative traits. For example, markers closely linked toalleles or markers containing sequences within the actual alleles ofinterest can be used to select plants that contain the alleles ofinterest during a backcrossing breeding program. The markers can also beused to select toward the genome of the recurrent parent and against themarkers of the donor parent. This procedure attempts to minimize theamount of genome from the donor parent that remains in the selectedplants. It can also be used to reduce the number of crosses back to therecurrent parent needed in a backcrossing program. The use of molecularmarkers in the selection process is often called genetic marker enhancedselection or marker-assisted selection. Molecular markers may also beused to identify and exclude certain sources of germplasm as parentalvarieties or ancestors of a plant by providing a means of trackinggenetic profiles through crosses.

Mutation breeding may also be used to introduce new traits into lettucevarieties. Mutations that occur spontaneously or are artificiallyinduced can be useful sources of variability for a plant breeder. Thegoal of artificial mutagenesis is to increase the rate of mutation for adesired characteristic. Mutation rates can be increased by manydifferent means including temperature, long-term seed storage, tissueculture conditions, radiation (such as X-rays, Gamma rays, neutrons,Beta radiation, or ultraviolet radiation), chemical mutagens (such asbase analogs like 5-bromo-uracil), antibiotics, alkylating agents (suchas sulfur mustards, nitrogen mustards, epoxides, ethyleneamines,sulfates, sulfonates, sulfones, or lactones), azide, hydroxylamine,nitrous acid, or acridines. Once a desired trait is observed throughmutagenesis the trait may then be incorporated into existing germplasmby traditional breeding techniques. Details of mutation breeding can befound in Principles of Cultivar Development by Fehr, MacmillanPublishing Company (1993).

The production of double haploids can also be used for the developmentof homozygous varieties in a breeding program. Double haploids areproduced by the doubling of a set of chromosomes from a heterozygousplant to produce a completely homozygous individual. For example, seeWan, et al., Theor. Appl. Genet., 77:889-892 (1989).

Additional non-limiting examples of breeding methods that may be usedinclude, without limitation, those found in Principles of PlantBreeding, John Wiley and Son, pp. 115-161 (1960); Allard (1960);Simmonds (1979); Sneep, et al. (1979); Fehr (1987); and “Carrots andRelated Vegetable Umbelliferae,” Rubatzky, V. E., et al. (1999).

Definitions

In the description that follows, a number of terms are used. In order toprovide a clear and consistent understanding of the specification andclaims, including the scope to be given such terms, the followingdefinitions are provided:

Allele. The allele is any of one or more alternative forms of a gene,all of which relate to one trait or characteristic. In a diploid cell ororganism, the two alleles of a given gene occupy corresponding loci on apair of homologous chromosomes.

Backcrossing. Backcrossing is a process in which a breeder repeatedlycrosses hybrid progeny back to one of the parents, for example, a firstgeneration hybrid F₁ with one of the parental genotypes of the F₁hybrid.

Bolting. The premature development of a flowering stalk, and subsequentseed, before a plant produces a food crop. Bolting is typically causedby late planting.

Bremia lactucae. An oomycete that causes downy mildew in lettuce incooler growing regions.

Corky root. A disease caused by the bacterium Rhizomonas suberifaciens,which causes the entire taproot to become brown, severely cracked, andnon-functional.

Cotyledon. One of the first leaves of the embryo of a seed plant;typically one or more in monocotyledons, two in dicotyledons, and two ormore in gymnosperms.

Essentially all the physiological and morphological characteristics. Aplant having essentially all the physiological and morphologicalcharacteristics means a plant having the physiological and morphologicalcharacteristics of the recurrent parent, except for the characteristicsderived from the converted gene.

First water date. The date the seed first receives adequate moisture togerminate. This can and often does equal the planting date.

Gene. As used herein, “gene” refers to a segment of nucleic acid. A genecan be introduced into a genome of a species, whether from a differentspecies or from the same species, using transformation or variousbreeding methods.

Heart. Heart is the portion in the center of romaine type lettuces wherethe leaf tips curve inward to cover the growing point. Cut and trimmedhearts of romaine type lettuces can be obtained by removing the frameleaves and cutting the stem off just below the base of the outermostheart leaf.

Heart diameter. Diameter of the cut and trimmed heart, slicedlongitudinally, and measured at the widest point perpendicular to thestem.

Heart length. Length of the cut and trimmed heart, slicedlongitudinally, and measured from the base of the cut stem to the top ofthe outermost heart leaf (along the longest possible aspect of theheart).

Heart weight. Weight of the cut and trimmed heart.

Lettuce die-back. A disease that can cause a stunted plant with yellowedouter leaves that can develop necrotic spots and lesions, and dark greeninner leaves that can be rough and leathery. Lettuce dieback is asoil-borne disease caused by two closely related viruses from the familyTombusviridae—Tomato Bushy Stunt Virus (TBSV) and Lettuce Necrotic StuntVirus (LNSV).

Lettuce mosaic virus. A disease that can cause a stunted, deformed, ormottled pattern in young lettuce and yellow, twisted, and deformedleaves in older lettuce.

Maturity date. Maturity refers to the stage when the plants are of fullsize or optimum weight, in marketable form or shape to be of commercialor economic value.

Nasonovia ribisnigri. A lettuce aphid that colonizes the innermostleaves of the lettuce plant, contaminating areas that cannot be treatedeasily with insecticides.

Quantitative Trait Loci. Quantitative Trait Loci (QTL) refers to geneticloci that control to some degree, numerically representable traits thatare usually continuously distributed.

Regeneration. Regeneration refers to the development of a plant fromtissue culture.

RHS. RHS refers to the Royal Horticultural Society of England whichpublishes an official botanical color chart quantitatively identifyingcolors according to a defined numbering system. The chart may bepurchased from Royal Horticulture Society Enterprise Ltd., RHS Garden;Wisley, Woking; Surrey GU236QB, UK.

Single gene converted. Single gene converted or conversion plant refersto plants which are developed by a plant breeding technique calledbackcrossing or via genetic engineering where essentially all of thedesired morphological and physiological characteristics of a line arerecovered in addition to the single gene transferred into the line viathe backcrossing technique or via genetic engineering.

Tip burn. Means a browning of the edges or tips of lettuce leaves thatis a physiological response to a lack of calcium.

Wet date. The wet date corresponds to the first planting date oflettuce.

Overview of the Variety ‘Roscoe’

Lettuce variety ‘Roscoe’ is a moderate yellowish green colored romainelettuce variety that is medium bolting and has a large, elongate shapedheart. ‘Roscoe’ is suitable for cultivation both in the greenhouse andin the open. In particular, lettuce variety ‘Roscoe’ is suitable forcultivation in hydroponic growing systems. The leaf texture of ‘Roscoe’is ideal for processing, and the vein structure of ‘Roscoe’ is ideal forpackaging. Lettuce variety ‘Roscoe’ is resistant to corky root(Rhizomonas suberifaciens); resistant to Bremia lactucae (downy mildew)races Bl-EU:16-26, 28, 31, 32, and Bl-US:1-9; resistant to lettucedie-back (TBSV), and resistant to Nasonovia ribisnigri biotype Nr:0.FIG. 1A shows the fourth leaf of lettuce variety ‘Roscoe’, FIG. 1B showsa top view of a plant with harvest-mature outer leaf of lettuce variety‘Roscoe’, FIG. 1C shows a dorsal view of a plant of lettuce variety‘Roscoe’, and FIG. 1D shows a longitudinal cross-sectional view of aharvest-mature plant of lettuce variety ‘Roscoe’. Lettuce variety‘Roscoe’ is the result of numerous generations of plant selectionschosen for its tolerance to tipburn, resistance to bolting, heartformation and size, harvest weight, crisp and moderately savoyed leaftexture, and moderately raised, strong and straight vein structure.

The variety has shown uniformity and stability for the traits, withinthe limits of environmental influence for the traits. It has beenself-pollinated a sufficient number of generations with carefulattention to uniformity of plant type. The line has been increased withcontinued observation for uniformity. No variant traits have beenobserved or are expected in variety ‘Roscoe’.

Objective Description of the Variety ‘Roscoe’

Lettuce variety ‘Roscoe’ has the following morphologic and othercharacteristics:

Plant type: Cos (i.e., romaine)

Seed:

Color: RHS 202C (Greenish grey)

Seed light dormancy: Light not required

Heat dormancy: Not susceptible

Cotyledon to fourth leaf stage

Shape of cotyledons: Intermediate

Cotyledon length: 9 mm

Cotyledon width: 7 mm

Shape of fourth leaf: Elongated

Fourth leaf length: 45 mm

Fourth leaf width: 30 mm

Apical margin: Crenate/gnawed

Basal margin: Moderately dentate

Green color: Medium green

Anthocyanin distribution: Absent

Cupping: Slight

Reflexing: None

Mature Leaves:

Incision depth: Absent/shallow

Indentation: Entire

Undulation of apical margin: Absent/slight

Green color: RHS 138A (Moderate yellowish green)

Anthocyanin distribution: Absent

Leaf glossiness: Glossy

Blistering: Moderate

Leaf thickness: 1 mm (intermediate)

Trichomes: Absent (smooth)

Plant:

Spread of frame leaves: 42 cm

Frame leaf length: 32 cm

Frame leaf width: 21 cm

Heart diameter (market trimmed with single cap leaf): 16 cm

Heart weight: 1000 grams

Heart shape: Elongate

Heart size class: Large

Heart firmness: Moderate

Heart filling percentage: 85%

Heart length: 28 cm

Butt:

Butt shape: Rounded

Midrib: Moderately raised

Core:

Core diameter at base of heart: 45 mm

Ratio of heart diameter/core diameter: 3.55

Core height from base of heart to apex: 80 mm

Bolting:

Number of days from first water to seed stalk emergence under summerconditions: 72

Class: Medium

Mature seed stalk height: 140 cm

Mature seed stalk spread: 22 cm

Spread of bolter plant at widest point: 25 cm

Bolter leaves: Curved

Margin: Entire

Bolter habit:

-   -   Terminal inflorescence: Present    -   Lateral shoots: Absent    -   Basal side shoots: Absent

Disease/Pest Resistance:

Corky root (Rhizomonas suberifaciens): Resistant Downy mildew (Bremialactucae) (Bl): Resistant to Bl-EU:16-26, 28, 31, 32, and Bl-US:1-9

Lettuce die-back (TBSV): Resistant

Nasonovia ribisnigri biotype 0 (Nr:0): Resistant

Stress resistance:

Tipburn: Tolerant

Heat: Susceptible

Cold: Resistant

Comparisons to Other Lettuce Varieties

Table 1 below compares characteristics of lettuce variety ‘Roscoe’ withthe lettuce variety ‘Arroyo’ (U.S. Pat. No. 9,198,394). Column 1 liststhe characteristics, column 2 shows the characteristics for lettucevariety ‘Roscoe’, and column 3 shows the characteristics for lettucevariety ‘Arroyo’. Further distinguishing features are apparent from thecomparison of the two varieties depicted in FIGS. 1A-1D and FIG. 2.

TABLE 1 Characteristic ‘Roscoe’ ‘Arroyo’ Tipburn tolerance More tipburntolerant Less tipburn tolerant (2 out of 5 heads examined (2-3 tipsburned within were tipburn free) every head examined) Heart length 28 cm23 cm

Table 2 below compares characteristics of lettuce variety ‘Roscoe’ withthe lettuce variety ‘Green Forest’ (U.S. Pat. No. 6,649,815). Column 1lists the characteristics, column 2 shows the characteristics forlettuce variety ‘Roscoe’, and column 3 shows the characteristics forlettuce variety ‘Green Forest’. Further distinguishing features areapparent from the comparison of the two varieties depicted in FIGS.1A-1D and FIG. 3.

TABLE 2 Characteristic ‘Roscoe’ ‘Green Forest’ Heart formation (closing)More heart Less heart formation (95%) formation (80%) Resistance toBremia lactucae Resistant Susceptible (downy mildew) races Bl-US: 9

Further Embodiments Gene Conversions

When the term “lettuce plant” is used in the context of the presentinvention, this also includes any gene conversions of that variety. Theterm “gene converted plant” as used herein refers to those lettuceplants which are developed by backcrossing, genetic engineering, ormutation, where essentially all of the desired morphological andphysiological characteristics of a variety are recovered in addition tothe one or more genes transferred into the variety via the backcrossingtechnique, genetic engineering, or mutation. Backcrossing methods can beused with the present invention to improve or introduce a characteristicinto the variety. The term “backcrossing” as used herein refers to therepeated crossing of a hybrid progeny back to the recurrent parent,i.e., backcrossing 1, 2, 3, 4, 5, 6, 7, 8, 9, or more times to therecurrent parent. The parental lettuce plant which contributes the genefor the desired characteristic is termed the “nonrecurrent” or “donorparent.” This terminology refers to the fact that the nonrecurrentparent is used one time in the backcross protocol and therefore does notrecur. The parental lettuce plant to which the gene or genes from thenonrecurrent parent are transferred is known as the recurrent parent asit is used for several rounds in the backcrossing protocol (Poehlman &Sleper (1994) and Fehr (1993)). In a typical backcross protocol, theoriginal variety of interest (recurrent parent) is crossed to a secondvariety (nonrecurrent parent) that carries the gene of interest to betransferred. The resulting progeny from this cross are then crossedagain to the recurrent parent and the process is repeated until alettuce plant is obtained where essentially all of the desiredmorphological and physiological characteristics of the recurrent parentare recovered in the converted plant, in addition to the transferredgene from the nonrecurrent parent.

The selection of a suitable recurrent parent is an important step for asuccessful backcrossing procedure. The goal of a backcross protocol isto alter or substitute a trait or characteristic in the original line.To accomplish this, a gene of the recurrent variety is modified orsubstituted with the desired gene from the nonrecurrent parent, whileretaining essentially all of the rest of the desired genetic, andtherefore the desired physiological and morphological, constitution ofthe original line. The choice of the particular nonrecurrent parent willdepend on the purpose of the backcross. One of the major purposes is toadd some commercially desirable, agronomically important trait to theplant. The exact backcrossing protocol will depend on the characteristicor trait being altered, which will determine an appropriate testingprotocol. Although backcrossing methods are simplified when thecharacteristic being transferred is a dominant allele, a recessiveallele may also be transferred. In this instance it may be necessary tointroduce a test of the progeny to determine if the desiredcharacteristic has been successfully transferred.

Many gene traits have been identified that are not regularly selected inthe development of a new line but that can be improved by backcrossingtechniques. Examples of these traits include, but are not limited to,male sterility, modified fatty acid metabolism, modified carbohydratemetabolism, herbicide resistance, resistance for bacterial, fungal, orviral disease, insect resistance, enhanced nutritional quality,industrial usage, yield stability, and yield enhancement. These genesare generally inherited through the nucleus. Several of these genetraits are described in U.S. Pat. Nos. 5,777,196, 5,948,957, and5,969,212, the disclosures of which are specifically hereby incorporatedby reference.

Tissue Culture

Further reproduction of the variety can occur by tissue culture andregeneration. Tissue culture of various tissues of lettuce andregeneration of plants therefrom is well known and widely published. Forexample, reference may be had to Teng, et al., HortScience, 27:9,1030-1032 (1992); Teng, et al., HortScience, 28:6, 669-1671 (1993);Zhang, et al., Journal of Genetics and Breeding, 46:3, 287-290 (1992);Webb, et al., Plant Cell Tissue and Organ Culture, 38:1, 77-79 (1994);Curtis, et al., Journal of Experimental Botany, 45:279, 1441-1449(1994); Nagata, et al., Journal for the American Society forHorticultural Science, 125:6, 669-672 (2000); and Ibrahim, et al., PlantCell Tissue and Organ Culture, 28(2), 139-145 (1992). It is clear fromthe literature that the state of the art is such that these methods ofobtaining plants are routinely used and have a very high rate ofsuccess. Thus, another aspect of this invention is to provide cellswhich upon growth and differentiation produce lettuce plants having thephysiological and morphological characteristics of variety ‘Roscoe’.

As used herein, the term “tissue culture” indicates a compositioncontaining isolated cells of the same or a different type or acollection of such cells organized into parts of a plant. Exemplarytypes of tissue cultures are protoplasts, calli, meristematic cells, andplant cells that can generate tissue culture that are intact in plantsor parts of plants, such as leaves, pollen, embryos, roots, root tips,anthers, pistils, flowers, seeds, petioles, suckers, and the like. Meansfor preparing and maintaining plant tissue culture are well known in theart. By way of example, a tissue culture containing organs has been usedto produce regenerated plants. U.S. Pat. Nos. 5,959,185, 5,973,234, and5,977,445 describe certain techniques, the disclosures of which areincorporated herein by reference.

Additional Breeding Methods

The invention is also directed to methods for producing a lettuce plantby crossing a first parent lettuce plant with a second parent lettuceplant where the first or second parent lettuce plant is a lettuce plantof variety ‘Roscoe’. Further, both first and second parent lettuceplants can come from lettuce variety ‘Roscoe’. Thus, any such methodsusing lettuce variety ‘Roscoe’ are part of the invention: selfing,backcrosses, hybrid production, crosses to populations, and the like.All plants produced using lettuce variety ‘Roscoe’ as at least oneparent are within the scope of this invention, including those developedfrom varieties derived from lettuce variety ‘Roscoe’. Advantageously,this lettuce variety could be used in crosses with other, different,lettuce plants to produce the first generation (F₁) lettuce hybrid seedsand plants with superior characteristics. The variety of the inventioncan also be used for transformation where exogenous genes are introducedand expressed by the variety of the invention. Genetic variants createdeither through traditional breeding methods using lettuce variety‘Roscoe’ or through transformation of variety ‘Roscoe’ by any of anumber of protocols known to those of skill in the art are intended tobe within the scope of this invention.

The following describes breeding methods that may be used with lettucevariety ‘Roscoe’ in the development of further lettuce plants. One suchembodiment is a method for developing variety ‘Roscoe’ progeny lettuceplants in a lettuce plant breeding program, by: obtaining the lettuceplant, or a part thereof, of variety ‘Roscoe’ utilizing said plant orplant part as a source of breeding material, and selecting a lettucevariety ‘Roscoe’ progeny plant with molecular markers in common withvariety ‘Roscoe’ and/or with morphological and/or physiologicalcharacteristics selected from the characteristics listed in the sectionentitled “Objective description of the variety ‘Roscoe’”. Breeding stepsthat may be used in the lettuce plant breeding program include pedigreebreeding, backcrossing, mutation breeding, and recurrent selection. Inconjunction with these steps, techniques such as RFLP-enhancedselection, genetic marker enhanced selection (for example, SSR markers),and the making of double haploids may be utilized.

Another method involves producing a population of lettuce variety‘Roscoe’ progeny lettuce plants, by crossing variety ‘Roscoe’ withanother lettuce plant, thereby producing a population of lettuce plants,which, on average, derive 50% of their alleles from lettuce variety‘Roscoe’. A plant of this population may be selected and repeatedlyselfed or sibbed with a lettuce variety resulting from these successivefilial generations. One embodiment of this invention is the lettucevariety produced by this method and that has obtained at least 50% ofits alleles from lettuce variety ‘Roscoe’. One of ordinary skill in theart of plant breeding would know how to evaluate the traits of two plantvarieties to determine if there is no significant difference between thetwo traits expressed by those varieties. For example, see Fehr and Walt,Principles of Variety Development, pp. 261-286 (1987). Thus theinvention includes lettuce variety ‘Roscoe’ progeny lettuce plantscontaining a combination of at least two variety ‘Roscoe’ traitsselected from those listed in the section entitled “Objectivedescription of the variety ‘Roscoe’”, or the variety ‘Roscoe’combination of traits listed in the Summary of the Invention, so thatsaid progeny lettuce plant is not significantly different for saidtraits than lettuce variety ‘Roscoe’ as determined at the 5%significance level when grown in the same environmental conditions.Using techniques described herein, molecular markers may be used toidentify said progeny plant as a lettuce variety ‘Roscoe’ progeny plant.Mean trait values may be used to determine whether trait differences aresignificant, and preferably the traits are measured on plants grownunder the same environmental conditions. Once such a variety isdeveloped, its value is substantial since it is important to advance thegermplasm base as a whole in order to maintain or improve traits such asyield, disease resistance, pest resistance, and plant performance inextreme environmental conditions.

Progeny of lettuce variety ‘Roscoe’ may also be characterized throughtheir filial relationship with lettuce variety ‘Roscoe’ as, for example,being within a certain number of breeding crosses of lettuce variety‘Roscoe’. A breeding cross is a cross made to introduce new geneticsinto the progeny, and is distinguished from a cross, such as a self or asib cross, made to select among existing genetic alleles. The lower thenumber of breeding crosses in the pedigree, the closer the relationshipbetween lettuce variety ‘Roscoe’ and its progeny. For example, progenyproduced by the methods described herein may be within 1, 2, 3, 4, or 5breeding crosses of lettuce variety ‘Roscoe’.

As used herein, the term “plant” includes plant cells, plantprotoplasts, plant cell tissue cultures from which lettuce plants can beregenerated, plant calli, plant clumps, and plant cells that are intactin plants or parts of plants, such as leaves, pollen, embryos,cotyledons, hypocotyl, roots, root tips, anthers, pistils, flowers,ovules, seeds, stems, and the like.

The use of the terms “a,” “an,” and “the,” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. Forexample, if the range 10-15 is disclosed, then 11, 12, 13, and 14 arealso disclosed. All methods described herein can be performed in anysuitable order unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate the invention and does not pose a limitation on the scope ofthe invention unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the invention.

While a number of exemplary aspects and embodiments have been discussedabove, those of skill in the art will recognize certain modifications,permutations, additions, and sub-combinations thereof. It is thereforeintended that the following appended claims and claims hereafterintroduced are interpreted to include all such modifications,permutations, additions, and sub-combinations as are within their truespirit and scope.

Deposit Information

Lettuce variety ‘Roscoe’

A deposit of the lettuce variety ‘Roscoe’ is maintained by Enza ZadenUSA, Inc., having an address at 7 Harris Place, Salinas, Calif. 93901,United States. Access to this deposit will be available during thependency of this application to persons determined by the Commissionerof Patents and Trademarks to be entitled thereto under 37 C.F.R. § 1.14and 35 U.S.C. § 122. Upon allowance of any claims in this application,all restrictions on the availability to the public of the variety willbe irrevocably removed by affording access to a deposit of at least 625seeds of the same variety with the National Collection of Industrial,Food and Marine Bacteria Ltd. (NCIMB Ltd), Ferguson Building, CraibstoneEstate, Bucksburn, Aberdeen, AB21 9YA, United Kingdom.

At least 625 seeds of lettuce variety ‘Roscoe’ were deposited on DATEaccording to the Budapest Treaty in the National Collection ofIndustrial, Food and Marine Bacteria Ltd (NCIMB Ltd), Ferguson Building,Craibstone Estate, Bucksburn, Aberdeen, AB21 9YA, United Kingdom. Thedeposit has been assigned NCIMB Number X1. Access to this deposit willbe available during the pendency of this application to personsdetermined by the Commissioner of Patents and Trademarks to be entitledthereto under 37 C.F.R. § 1.14 and 35 U.S.C. § 122. Upon allowance ofany claims in this application, all restrictions on the availability tothe public of the variety will be irrevocably removed.

The deposit will be maintained in the NCIMB depository, which is apublic depository, for a period of at least 30 years, or at least 5years after the most recent request for a sample of the deposit, or forthe effective life of the patent, whichever is longer, and will bereplaced if a deposit becomes nonviable during that period.

1. A lettuce seed designated as ‘Roscoe’, representative sample of seedhaving been deposited under NCIMB Accession Number X1.
 2. A lettuceplant produced by growing the seed of claim
 1. 3. A plant part from theplant of claim
 2. 4. The plant part of claim 3, wherein said part is aheart, a leaf, or a portion thereof.
 5. The plant part of claim 4,wherein said part is a heart.
 6. A lettuce plant having all thephysiological and morphological characteristics of the lettuce plant ofclaim
 2. 7. A plant part from the plant of claim
 6. 8. The plant part ofclaim 7, wherein said part is a heart, a leaf, or a portion thereof. 9.The plant part of claim 8, wherein said part is a heart.
 10. An F₁hybrid lettuce plant having ‘Roscoe’ as a parent where ‘Roscoe’ is grownfrom the seed of claim
 1. 11. A pollen grain or an ovule of the plant ofclaim
 2. 12. A tissue culture of the plant of claim
 2. 13. A lettuceplant regenerated from the tissue culture of claim 12, wherein the planthas all of the morphological and physiological characteristics of alettuce plant produced by growing seed designated as ‘Roscoe’,representative sample of seed having been deposited under NCIMBAccession Number X1.
 14. A method of making lettuce seeds, said methodcomprising crossing the plant of claim 2 with another lettuce plant andharvesting seed therefrom.
 15. A method of making a lettuce variety‘Roscoe’, said method comprising selecting seeds from the cross of one‘Roscoe’ plant with another ‘Roscoe’ plant, a sample of ‘Roscoe’ lettuceseed having been deposited under NCIMB Accession Number X1.